This invention provides a method and apparatus for transmitting and receiving data derived from an electromagnetic waveform and for analyzing and displaying the information. More specifically, the invention relates to the encoding, transmission, reception and decoding of information to recover the parameters of an electromagnetic waveform, i.e., one representing an electrocardiogram, in real time.
It is known in the art to transmit data derived from electronic waveforms such as from the electrocardiogram of a medical patient from a remote location in which the patient is situated to a central station where a physician is resident. Such apparatus is employed by paramedics who can transmit the electrocardiogram of a patient in distress to a physician at a central station, thereby enabling a single phYsician to monitor a relatively large geographic area through the use of paramedic personnel who need only be trained to apply an ECG measuring apparatus to the patient.
It is further known in the art to encode a continuous signal of varying amplitude into a continuous constant amplitude signal having a frequency which varies in proportion to the amplitude of the original signal. Frequence modulation, as this technique is known, is widely used in communications transmissions over the air or telephone lines. It is further known to recapture the information encoded on a frequency modulated constant amplitude continuous, e.g., sinusoidal, signal by demodulating the fm signal. For example, analog signal frequency modulationdemodulation is performed routinely in the transmission and reception of radio and television broadcast programming.
Analog fm demodulators are complex and prone to errors caused by analog component parameter drift and the introduction of delays due to inertial characteristics of necessary filters employed in analog circuitry.
The present invention overcomes the limitations of the prior art in providing for a method which can be economically implemented in apparatus to allow for interpretation of an fm signal by converting it to digital form, processing it, and reconstructing informational characteristics of the analog signal used to modulate the fm signal, in real time on a constructed simulation of the original signal through the use of standard circuitry readily found in a personal digital computer which can be configured according to the invention and operated and maintained with minimal training and expense.